ECiCylinderHeadFailuresonContinentalIO520&550EnginesBriefingforDorendaBakerJune16,2013ChipQueitzschCSTAWayneMaguireANECylinderHeadFailures•CylinderheadfatiguefailureisahistoricalfailuremodeforGAreciprocationengines–RateshaveimprovedsignificantlywithOEMdesignrefinements•Cylinderconstruction:Aluminumheadthreaded/shrinkfittosteelcylinderbarrel•Fatiguelifeofcylinderheadcontrolledbyinstallationshrinkfitandlocalfeaturegeometry•Typicalfailuresiteintopthreads•Operatingconditionscanhaveadverseeffectonheadfatiguelife•OEMandPMAcylindersareoperatedsimilarlyBarrelCylinderHeadFailureSiteECiPMADesignDeficiencies•Concernsregardingrigorinreverseengineeringofgeometry/fitsandvalidationofdesign:–HeadshrinkfitlessthanTC’ddesign–Stressrelevantfeaturesnotcopiedprecisely(radii,wallthickness)•ECihasincrementallyincreasedshrinkfitinrecentyears•Fieldserviceindicatesincrementalreductionsinfailurerate•CurrentshrinkfitstillallowsassemblylessthanTC’ddesign•AEC/ECirecentlycontractedforanalysissupport–Analysisidentifiesshrinkfitcriticality–Analysisalsoidentifiesoperationtemperatureasapotentialcontributingfactor–IfPMAcylindersaccuratelyreplicatedtheTC’ddesignandpiloterrorweretherootcause,thenTCandPMAcylindersshouldhavesimilarfailurerates!•Applicantclaimsoriginalshrinkfitcanbeestablishedfromdisassembledneworusedparts–ButapplicantdoesnotacknowledgewhethertheyhaveorhavenotmeasuredTC’dpartstocheckTC’ddesignshrinkfitCylinderHeadFailureRateTheECifailurerateis32timeshigherthanContinental’sTCM=ContentalMotorsPropulsionSystemStructuralFailureandGAAccidents/FatalitiesPropulsionSystemStructuralFailureisthe#2causeofGAminorandseriousinjuriesand#3causeofGAfatalitiesECiRebuttalsPlacedinPerspective•“Rootcauseisoperatorerror”(overtemperature)–FALSE:ECiandTCcylindersareoperatedsimilarly,butECifailurerateis32xgreater.(OTexacerbatesinadequateshrink)•ECihasfewerfailuresrelativetoContinental(pitchtoNTSB)–MISREPRESENTSFACTS:ECifailurerateis32xworsethanthecurrentTC’ddesignOldTCHdesignsareretired(AD’d),currentdesigniscomparisonbasisRiskAssessment•Useoftypicalrisktoolslimitedbyincompletefielddata...primaryissueisunder‐reportedevents.•Highrelianceplacedoneventscatterplotandfailurerateineachpopulation(onlyusingreportedevents)•ResultingADdecisionconsistentwithrecipengineriskpolicy(PS‐ANE‐100‐1999‐00006).–SameresultwithandwithoutconsiderationofBahamafatalaccidenttriggeredbyECicylinderfailure.(NOTE:RecippolicydoesnothaveaCAAMstylestatisticalassessment)•ResultingADisalsoconsistentwithearlierECiandotherenginecylinderADsissuedsince2005.–Examples:2009‐26‐12,2009‐19‐07,2009‐16‐03Recommendation•TheproposedADofECicylindersproducedpriortothe2009shrinkfitchangeiswarranted•FieldserviceshowsECifailurerateis32xhigherthantheTC’ddesign•AtleastoneforeignfatalaccidentassociatedwiththeECiPMAdesign•FAAGASafetyStudyshowsPropulsionSystemstructuralfailuresarethe#3causeoffatalitiesand#2causeforseriousandminorinjuries•RequirementsintheRecip policyforissuinganADaremet•EarlierTCandPMAdesignswithsimilarorgreaterfailurerateshavebeenAD’d•Maindifferenceforthisactionisthegreaternumberofenginesaffected(largerfleetsizeandmagnitudeofECipresenceinfleet)•ECiargumentagainstADbasedonnofailuresinnewproductionbutthisignoresthethreattotheinservicefleetwithpre‐2009cylinders(enginessubjecttotheAD)